Our investigations are based on the following picture of acetylcholine action at the frog neuromuscular junction: Agonist binds rapidly to the receptor and induces a conformational change to open an associated channel. Because of a dipole moment change associated with the open-closed transition, the channel closing and opening rates are influenced by membrane potential. We hope to refine and extend this view during the upcoming grant period. More specifically, we will use the voltage clamp technique to (1) examine and analyze dose-response curves to obtain information about the agonist binding process, (2) analyze actions of prostigmine on channel kinetics with fluctuation analysis, (3) investigate the mechanisms by which the average single channel conductance depends on the nature of the agonist used, and (4) study certain complexities in channel gating that have been found in Rana temporaria.